Combustion and vibration characteristics of variable compression ratio direct injection diesel engine fuelled with diesel‐biodiesel and alcohol blends

Abstract The objective of the present investigation is to explore the influence of ternary (diesel‐biodiesel‐alcohol) fuel blends on the combustion and vibration parameters of a variable compression ratio compression ignition engine. Kusum seed oil biodiesel and isobutyl alcohol were blended with conventional diesel to make a ternary fuel. The blend of biodiesel‐diesel (B20) was made in proportion of 20% and 80% by volume, respectively. Furthermore, isobutyl alcohol was added at diverse proportions (ie, 0.25%, 0.5%, 0.75%, and 1%). The investigation was carried at different compression ratios (CRs), namely, 16.5, 17.5, and 18.5. The study shows that, upon the addition of isobutyl alcohol, the combustion characteristics (ie, cylinder pressure [CP] and net heat release rate [NHRR]) are significantly enhanced, whereas the mechanical vibration level maintains stable. The CP and NHRR of B20+ 1% isobutyl alcohol are greatly improved for corresponding values of 4.55% and 8.39%, respectively, except for the conventional diesel at CR 18.5. Furthermore, the root mean square velocity (vibration) decreases when increasing the quantity of isobutyl alcohol and attained a minimum with B20+ 1% isobutyl alcohol. The experimental results show that the isobutyl alcohol up to 1% with diesel‐biodiesel blends can be used in the CI engine with no further adjustments.